One known method for improving the smoothness of textile fibers is so-called dry paraffinizing. In this process, the yarn to be treated is guided over solid paraffin during winding. Through abrasion, the filament takes up paraffin in a quantity governed by the type of paraffin used, the contact pressure and the rate of travel of the filament.
Unfortunately, this process is attended by serious disadvantages. Thus, to ensure frictionless further processing of the textile material, the paraffin has to be applied in a precisely defined quantity; different types of paraffin being used according to the time of year. During winding, the normal winding speed has to be reduced by 20 to 25%. In addition, suitable temperatures have to be maintained for storing the paraffinized packages of wound yarn.
In the processing of yarns, particularly single yarns, yarn dragging and filament breakages can occur during the paraffinizing treatment. Another disadvantage lies in the possible efflorescence of the paraffin during subsequent steaming and ironing processes.
In addition, dry paraffinizing is generally not sufficient for imparting a good handle to the material. This requires an additional treatment with a standard cationic softening agent.
U.S. Pat. No. 4,122,018 describes preparations based on aqueous paraffin dispersions which are suitable for treating a variety of different textile fibers, such as cellulose fibers, wool fibers, synthetic fibers, or mixtures thereof, and which impart to fibers such as these the smoothness required for further processing and good handle. However, practical experience has shown that yarns of cotton or of cotton/synthetic fibers cannot always be readily treated with wet-paraffinizing agents of the type described in U.S. Pat. No. 4,122,018 without additional hard paraffinizing.
Another important function of textile smoothing agents is to impart satisfactory stitchability to sheet-form textile materials, particularly knitted and woven fabrics. If excessive frictional forces occur during stitching, stitching damage is caused when the filaments are struck or crushed by the needles or suffer heat damage. The consequences of stitching damage are particularly serious in the case of knitted fabrics because the fabrics develop ladders upon mechanical stressing. It is crucially important for the filaments to be able to move within the knitted structure of the fabric. Reduction of the needle penetration forces during stitching on modern high-speed sewing machines has acquired particular significance because machines of this type are mechanically capable of completing up to 7000 stitches per minute. However, this requires more vibration-resistant and hence thicker needles from which the stitches are more easily damaged.